Turbine blade lock



June 28, 1960 J. R. HAYES 2,942,842

TURBINE BLADE LOCK Filed June 15, 1956 N VEN OR.

United States Patent TURBINE BLADE LOCK John R. Hayes, Indianapolis, Ind., amignor 'to General Motors Corporation, Detroit, Mich, a corporation of Delaware v 'My invention relates to wheel and blade assemblies such as are use-din axial flow compressors and turbines and is particularly directed to providing an improved means of retention of blades on wheels.

' By way of background, it maybe pointed out that axial flow compressors and turbines commonly are made up of one or more wheels, each of which has a number of blades mounted around the rim of the wheel. Commonly, the wheel has slots cut across the rim into which the blades are inserted, there being some form of dovetail engagement between the root of the blade and the walls of the slot. Usually, the blades are retained from sliding out of the slots by some structure which keys or pins the blades to the wheel. Perhaps the most common mode of retention involves the use of a pin which extends more or less radially through the wheel rim into the base of the blade. Other structures which have been proposed (see, for example, U.S. Patents 2,434,935 and 2,686,656) involve keys which lie under the base. of the blade at the bottom of the blade slot and are fixed in some way to the wheel and blade. While such structures may provide adequate blade retention, they have the disadvantage that they weaken the wheel at a point of very high stress at the blade root, with the result that the entire wheel must be made heaw'er than would otherwise be necessary.

In distinction to these prior proposals, the blade locking structure of the present invention involves structure disposed at the rim of the wheel between the blade slots -in a region of low stress, with the result that the weight of the wheel and, consequently, of the other parts of the engine, need not be increased to compensate for stress inducing conditions presented by blade locking means located at the bottom of the blade slot.

The principal objects of the invention are to provide an improved turbine wheel assembly; to decrease the weight and increase the strength of such assemblies; to provide a turbine wheel and blade assembly with locking means which is readily applied and removed and does not weaken the wheel; and to provide a simple, effective, and convenient blade locking means for such installations.

'The nature of the invention and the advantages thereof will be clearly apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings in which:

Fig. 1 is a fragmentary perspective view of a wheel and blade assembly according to the invention;

Fig. 2 is a sectional view of the same taken on a plane containing the axis of the turbine wheel, as indicated by the line 2-2 in Fig. 1;

Fig. 3 is a sectional view taken on a plane at right angles to the blade slots, as indicated by the line 3-3 in Fig. 2; and

Fig. 4 is a perspective view of the blade retaining key.

The invention is shown and described herein as applied to a typical turbine structure and the structure hereinafter will be referred to as a turbine, but the term is not intended as one of limitation, since the invention is readiticular slot and root form is immaterial.

-Patented June 28, 1960 it may follow any suitable known configuration and the invention is not concerned with the disk or hub of the wheel. Blades 12 are mounted in the Wheel, each blade comprising an airfoil or blade portion 13, a root 14, and a blade platform 15, projecting circumferentially of the wheel immediately adjacent the rim thereof, between the blade portion and root portion of the blade. As illustrated, the blade roots are of the common multiple dovetail form and are mounted in the multiple serrated slots 17 in the rim of the wheel. It will be understood that the par- These slots extend across the rim from the forward face 18 of the wheel to the rearward face 19 thereof.

The wheel illustrated is one in which the periphery of the'wheel is conical or tapered, in which case the serrations on the whee'l and blade root are likewise at an angle to the axis of the wheel, which axis may be considered as horizontal in Fig. 2. The invention is particularly desirable in connection with a coned wheel, but is not limited thereto. Ordinarily, the blade rootsar'e a slightly loose fit in the slots in the turbine wheel. The blades are mounted by sliding them axially of the wheel into the grooves.

It will be understood that the structure so far described is old and Well known. In connection with prior structures, however, it has been customary to extend a pin through the rim 11 of the wheel into the blade root 14 or to dispose retainers in the bottom of the groove 17. Structures of both these types weaken the wheel at the base of the groove, which is a point of high stress.

The blade retaining or locking means of the present invention comprises keys 20 which, as will be most clear 1y apparent from Figs. 3 and 4, are tapered longitudinally or from end to end with the thin end of the key adjacent the larger diameter face 18 of the wheel, which is the forward face in this example. The major portion of the tapered body 20' of the key is approximately of the form of 21.120 sector of a circle in cross section, as shown most clearly in Fig. 3. The upper face of the body is defined by two surfaces 21 and 22 which lie beneath and substantially parallel to the under surfaces of the blade platforms 15, which incline outwardly from the blade root. The generally cylindrical under surface 23 of the key lies in a complementary groove 24 in the rim of the wheel, the groove being disposed in the projecting part of the wheel rim between the blade slots. The key is a single integral piece including a generally rectangular head 26 at the thicker and of the body, the head 26 extending inwardly and circumferentially from the body and being adapted to abut the face 19 of the wheel. The other end 27 of the key, which is flat and relatively thin, defines a deformable portion which may be bent inwardly from its original form, illustrated in Fig. 4 and by the broken lines in Fig. 2, to provide a head 28 abutting the face 18 of the wheel. The key is thus retained against displacement axially of the turbine or transversely of the wheel rim by the heads 26 and 28.

The blade is interlocked with the key to hold the blade against axial displacement by the interengagement of abutments defined by a lug or projection 31 extending radially outwardly from the body of the key and a notch 32 in one of the adjacent blade platforms receiving the lug. As will be apparent, the key is retained against moving radially out of the assembly by the fact that it is lodged under the blade platforms.

With a tapered wheel, there is a very substantial force urging the blade to the left as shown in Fig. 2 because 

